Downgrading Proxmox OS installation 7.0-8 to 6.X

[proxmpadawan]

Hello,

Apologies if this topic was covered elsewhere, I just could not seem to find the topic in the search.

About a month ago I installed not upgraded, installed fresh Proxmox 7.0 and all was fine until I decided to virtualize a plex server using Ubuntu server 20.04 with my Nvidia 1660 for hardware acceleration.

I used well documented settings for PCIe passthrough and overall it has worked except that when the graphics card starts transcoding the fans stop functioning. Without fail the GPU fans are stable from 21-24% fan use according to nvidia-smi after a reboot but when transcoding takes place they go down to 0% and never come back up.

I also have networking issues. My intel-x520-da2 does not seem to work well as it consistently maxes out at 192 Mbps during file transfers but that could just be the HDD bottleneck.

This is just an exercise in trying to rule out the proxmox version being the issue.

Does anyone know if it is possible to Downgrade from one version of Proxmox to another when there was never an actual upgrade. I saw a lot of posts on rolling back but nothing on downgrading, also I may be using the wrong terminology.

If anyone has any ideas please let me know.

Otherwise I will have to just backup my vm's and do a fresh install of a 6.X version.

All the best,
P
PS this is a non-subscription version

 

[t.lamprecht]

Hi,

Does anyone know if it is possible to Downgrade from one version of Proxmox to another when there was never an actual upgrade. I saw a lot of posts on rolling back but nothing on downgrading, also I may be using the wrong terminology.

It's not completely impossible, not much is, but it's also pretty close.
Downgrade a single package can work out, especially if the new and old package version have both the exact same dependency constraints.

But a full system downgrade to an older major release is something else, to make it short quote from the Debian wiki article:

Is it supported?​

• Short answer: No, it isn't supported.
• Long answer: It isn't supported because
  1. The packages' installation scripts (postinst...) are designed to handle upgrade only.
  2. The installation tools are designed to replace older versions of packages by newer versions.

-- https://wiki.debian.org/SystemDowngrade

So I only would go for that if one would be really desperate, but as we highly recommend doing backups in general, and all the more recommend testing those before major upgrades, it should normally be possible to reinstall;

I used well documented settings for PCIe passthrough and overall it has worked except that when the graphics card starts transcoding the fans stop functioning. Without fail the GPU fans are stable from 21-24% fan use according to nvidia-smi after a reboot but when transcoding takes place they go down to 0% and never come back up.

Motherboard and GPU firmware are up-to-date? Not sure how much the PVE host or its version can be assigned fault in this case; as that's rather something the guest OS controls after the GPU was passed through.

I also have networking issues. My intel-x520-da2 does not seem to work well as it consistently maxes out at 192 Mbps during file transfers but that could just be the HDD bottleneck.

You could use iperf to better test that while ruling out disk IO.

 

[proxmpadawan]

Hi,


It's not completely impossible, not much is, but it's also pretty close.
Downgrade a single package can work out, especially if the new and old package version have both the exact same dependency constraints.

But a full system downgrade to an older major release is something else, to make it short quote from the Debian wiki article:


-- https://wiki.debian.org/SystemDowngrade

So I only would go for that if one would be really desperate, but as we highly recommend doing backups in general, and all the more recommend testing those before major upgrades, it should normally be possible to reinstall;


Motherboard and GPU firmware are up-to-date? Not sure how much the PVE host or its version can be assigned fault in this case; as that's rather something the guest OS controls after the GPU was passed through.


You could use iperf to better test that while ruling out disk IO.

@t.lamprecht

Thank you for your reply. I will respond in a backwards fashion as that's probably the most relevant at this point. I did try iperf3 in the past and saw an average throughput of 17.3 Mbps. But I actually just tried removing the intel sfp+ and adding a third party DAC connection and throughput just went up to 8 Gbps. So PVE was not at fault there, but I would like to know if there is a way to optimize to have it go to 9 Gbps at least. The intermediary switch is a mikrotik 4 port 10G switch. Then again, it could be the 3rd party DAC (ipolex).

I will revert back with any motherboard updates as I have 3 VMs running and being used at the moment.

I think it is probably best just to re-OS if necessary in the future but I am glad to learn that this is a legitimate question that has been addressed, thank you for the links.

Best,
P